This invention relates to the thermal insulation of an aircraft fuselage.
The fuselage of an aircraft is enclosed by an outer shell, and in the past this outer shell has generally included a metal outer skin supported around a metal frame consisting of stringer and circumferential members. Since temperatures within the fuselage must usually be controlled in order to insure a proper environment for occupants and cargo, most fuselage shells also include some form of thermal insulation. In many aircraft this insulation takes the form of fiberglass batts supported by the stringer and circumferential members, but a variety of other arrangements have also been employed with varying degrees of success. One such arrangement, for example, is disclosed in U.S. Pat. No. 3,867,244 to Clarence R. Adams.
Whatever type of insulation is utilized as part of the aircraft fuselage it is important that it be protected from condensate which may be present in large quantities. If the insulation is allowed to soak up significant amounts of this condensate the effectiveness of the insulation will be impaired, and thus, for example, where fiberglass batts are used they are generally treated to repel moisture. It is also desirable to prevent moisture from passing through the insulation and dripping or running into the passenger compartment, and so some provision must be made for handling liquid in or adjacent the shell.
Another consideration relative to insulation of the fuselage is that access to both sides of the shell must be provided for inspection purposes. Since virtually the entire outside surface of the shell is exposed, inspection of the outside of the shell presents no problem, but inside surfaces of the fuselage skin are not as accessible. Normally, where insulation batts are utilized as part of the inside of the shell they are readily removable to expose adjacent surface portions of the fuselage skin for inspection.
In some cases a fuselage shell may have an inside wall including substantial portions whose surfaces are not interrupted by structural members or other parts attached thereto. For example, a fuselage shell could be constructed using a sandwich panel comprising inner and outer metal skins on either side of a honeycomb core so that all strengthening members external to the sandwich panel such as stringers and circumferentials are eliminated. With this type of construction batts of insulation generally cannot be used since there are no members for conveniently supporting them, and a new arrangement for efficiently insulating the fuselage while allowing necessary inspection and providing for the presence of condensate is therefore required.